Feed and load units of this type are intended for removing in a short time in the machine tool the finished work pieces from the machining chamber, and to load a new work piece in the machining chamber for machining.
In this connection the term “load unit” has to be understood as generic term for loading and unloading, respectively, that is feeding and removing of work pieces to and from the machine tool.
Usually, in the state of the art the work pieces are arranged on a work piece carrier that can move on a guide path. It is possible here, that a work piece carrier can carry only exactly one or also several work pieces (even different work pieces). It is tantamount here, whether the work piece/s is/are arranged directly on the work piece carrier, or the work piece/s is/are attached to a work piece pallet, and thus the work piece is supported indirectly on the work piece carrier.
Usually, on the guide path at least two movable work piece carriers are located, wherein, seen in conveying direction of the work pieces, the first work piece carrier serves for removing the finished work piece from the machine tool, and the second work piece carrier, arranged behind it, feeds the next work piece to be machined. Depending on the dimensioning of the guide path or the feed and load unit, it is, of course, also possible, that more than two, for example three, four or even more work piece carriers are on the guide path.
The guide path serves for conveying the work piece carriers, and is configured, for example, extending straight and/or curved.
In the state of the art the arrangement is configured such that the work piece carrier feeds in a suitable way the work piece to the machine tool, then, during the work piece change phase, hands the work piece in the machining chamber, or picks up the finished work piece and removes it from the machining chamber. The work piece carrier is here only during a rather short period of time in the machining chamber, namely only for picking up or putting on the work piece. The machining chamber is adapted and optimized perfectly to the size of the work piece to be machined. If the work piece carrier remains during machining in the machining chamber, precious space would be wasted. Therefore, usually the guide path is arranged next to the machine tool, and the work piece carriers each are arranged such that they hand the work piece from the guide path in the machining chamber, or shift it back. For this motion a separate drive is required that is arranged at each work piece carrier.
This leads to a rather large effort as the drive at the first work piece carrier serves only for unloading, i.e., taking the finished work piece out of the machining chamber, and the drive at the second work piece carrier is only used for loading the work piece, respectively.
Furthermore, an appropriate power supply has to be provided for the drive traveling together with the work piece carrier, what can basically be realized with appropriate drag chains and the like, but is appropriately expensive. Besides the corresponding cost, here also the required space for this power supply has to be taken into consideration. In addition to that, the drive itself requires space on the work piece carriers, that might be required for conveying the work piece.